Solar cells, whether singly or connected in an array, have been utilized to supply power in a wide variety of applications. Those applications for which solar power may be utilized encompass virtually any device or system which utilizes electric power, and range from terrestrial uses in solar powered vehicles and hot water heaters to extraterrestrial uses in spacecraft. Because of the increasing importance and employment of solar generated power, it is necessary to make the most cost effective and efficient utilization of the power generated by a solar array. This is particularly true in applications where size and weight are significant concerns, such as in terrestrial vehicles or spacecraft in which the size and weight of solar panels contributes significantly to the size and weight of the overall system.
Effective utilization of the power generated by a solar cell array requires that the solar array be controlled to operate at its most efficient point. The most efficient operating point of a solar cell or solar cell array may vary dependent upon a variety of factors including temperature, illumination level, the type of cell, radiation damage to the cell, the number of cells in series and other cell properties. In general, the solar cell array will operate at its most efficient point and output the greatest amount of power at a specific power maximizing voltage which is determined by the operating conditions.
One such system for determining the power maximizing voltage of a solar cell array string operates by sensing the power at the output of a solar cell array before a signal indicative of power has propagated through the power tracking circuitry of the system. Since there may be losses in the tracking circuitry which would move the peak power point for the whole system, these losses can not be taken into account by such a system.
Another known system controls a large number of solar array strings grouped together as one. Since each individual solar array string has its power output maximizing voltage determined by different factors, the best peak power point for the group of solar array strings is necessarily less than the peak power outputs of the individual strings when each string is operated at its own output maximizing voltage.
Another known category of peak power trackers utilizes various analog techniques to approximate the peak power point of each solar array string. However, according to this category of power maximizing system each peak power tracker is an independent unit having logic circuitry required to peak power track the individual string the unit is controlling.